1. Field of the Invention
The present application relates to a laser system, in particular, relates to a wavelength tunable laser system.
2. Background Arts
A laser module that implements a wavelength tunable laser diode (t-LD) accompanies with a wavelength detector, or a wavelength locker to tune an emission wavelength of the t-LD. A t-LD often accompanies with a semiconductor optical amplifier (SOA) to amplify light generated in an LD having a wavelength tunable function, because the light output from the LD with the wavelength tunable function is often limited in output power thereof The SOA is usually integrated with the LD with the wavelength tunable function.
The wavelength detector, or the wavelength locker, implements an optical component inherently showing a specific transmittance, typically an etalon filter. Detecting a magnitude of raw light not passing the etalon filter and that of filtered light passing through the etalon filter, and comparing a ratio of the magnitude of the filtered light to that of the raw light with the transmittance of the etalon filter, the wavelength of the raw light, namely, the wavelength of the light currently emitted from the LD may be estimated. The wavelength tunable module may tune the emission wavelength thereof so as to coincide the current emission wavelength thus estimated with the target wavelength.
Recent optical communication systems request five or more figures in the preciseness of the signal wavelength. An optical module implementing a t-LD therein applicable to such communication system inevitably implements the superior exactness of the emission wavelength by a compact arrangement and simplified procedures.